Overload circuit breaker



' 'lll/III George E. Kirkby JNVENTOR.

BY MMLW Patented Jan. 2, 1951 Ul.\l;I1'l7ED-` STATES PATENT O FFICE IOVER'IKBAD CIRCUIT BREAKER `George Ei Kirkby, Louisville,.Ky.

Application 'J anuary 28, 1948, Serial No.l l882 (Cl. 20W-115.5)

4 Claims. 1..

The present invention relates to a safety-type overload make andbreakapplance, a. small and handy device constructedV with a pair of outstandingprongs. which may`r` be. conveniently plugged into aconventionalwallor floor receptacle and which is properly.y constructedto deliver a predeterminedamount offhouse'. current to the plug equipped cord of a fractionalhorsepower motor or any similar. electrical.. device: that may become ruinously overloaded.

More specically,the invention has` to do with a simple, economical and efficient safety appliancecharacterizedgby thestated prongs to fit into the usual house current receptacle, the same having an incorporated or built-in receptacle toraccommodatev a pronged plug for delivering the current to the motor or other electrical device and further havinga switch and thermal responsive means for-opening said switch upon the occurn rence of an overload of incoming current.

Another object of theinvention is to provide a practicaloverload current breaker of` the type generallyl referred to aboverwhicnthrough the instrumentality` of novel thermal responsive means automatically opens the switchl and cuts off the current as soon as the incoming current exceeds ten amperes.

A further object of the invention is to provide a novel overload breaker along the lines briefly described wherein cam means serves to open the safety switch and holds same open and wherein the thermal element, a bi-'metai element, func-'- tions as a releasing dogor trip, and wherein an accessible knob is handily adapted t re-set the switch to closed position once the thermal element returns to its normal cam retaining position.

Other objects,"fe`atures and advantages of the invention will'become more readily apparent from the following description and the accompanying illustrative drawings. Y

In the drawings, wherein like numeralsar'eemployed to designate like parts; throughout' the views:

Figure l a frontviewwtna portion of" the cover or casing broken'awayto clearly'expo'se the principal parts'of the 'internal mechanism;y

Figure 2 isa vertical sectional'view'takenon the irregular line 242 "of Figure'lf looking inthe direction oi'the arrows,

Figure 3 is a frontor face elevational view on a smallerk scale,

Figure' 4 is a 'cross section bn the line 4;4 of Figure -1, looking in the direction ofthel arrows,

vFigure` 5 isa fragmentary section taken `approximately on thev plane-of -the line .5;5 of Figure l, looking-in the-directioirofthearrows; and,"

Figure v6 isa perspective view of therelease and re-set cam.

Referring now to the drawings by distinguish# ing reference numerals, the base means 8 is made up lof a main rectangular base plate 9 superim posed'on a slightly largerr secondary or auxiliary base plate I0. A shell-like casing or cover is denotedby the numeral II and has a marginal rim I2 which surrounds the marginal edges of the main base 9 and rests'rmly against the project ing marginal edge portions of the secondary base plate IQ. rilhe cover is held frictionallyv in place, assisted by simple fastening means. The lattei means comprises a centrally arranged assembling block I3- which as best shown in Figure 2 has a central screw threaded vbore to accommodate an assembling screwv Id'which is passed through a boss I5 on the cover and is threaded into the block. A similar fastening screw I6 from the op posite or base side passes through the base plates I0 and 9 and is threaded into the opposite end of the bore in said `block I3. Attention is directed to anv L-shaped bracket IT which has a lateral attaching end I8 and this is apertured to permit passage of the bolt or screw I6 in the manner shown. The auxiliary base plate Iii is a removable part, that is, is detached from the base 9 and cover and serves to anchor the countersunk head of thescrew I6. This permits the plate IG to serve as an appropriate wall protector shield. The face of `the cover is provided with a depression I9 with slots 20 to accommodate'the prongs on a current take on plug (not shown). There is another depression ZI formed in the cover plate which serves to accommodate the hub portion of a re-set knob 22. The stated knob is provided with an indicator 23 to register with suitable off and on inscriptions 24 and 25 provided on the cover, as shown in Figure 3. The knob 22 is fastened on a shaft 26 which is mounted for rotation in a bearing in the L -shaped bracket Il and is also mounted in a suitable socket provided therefor, as at 21, on the main base plate rI'he aforementioned release and re-set carn is denoted by the numeral 28 and is a block of insulation and is keyed on the shaft 26 for rotation with latter. At one end is a wedge-like cam 29 and at the opposite end is a shoulder 35i which constitutes a detent.

Before proceeding further with the purely mechanical features and parts, I will now touch upon the electrical equipment. Referring then to Figure l the L-shaped element seen at the left and denoted by the numeral SI is a terminal and has a prong 32 which extends outwardly through apertures inthe base plates, as shown better in with said first-named plate and provided with an output prong, a current conducting heater element attached at one end to said primary terminal plate and attached at its opposite end to the secondary terminal plate, a longitudinally bowed bi-metallic element, constituting a trip latch, said element being fastened at one end to said secondary terminal plate, the opposite end being free and constituting the trip latch proper,

said bi-metallic element being disposed in close proximity to and in longitudinal alignment with said heater element, a block-like member mounted for oscillation on said base and having a cam at one end and a detent at an opposite end, said detent being releasably engageablewith said trip latch, a coiled spring attached at one end to the detent equipped end of said block-like member, the opposite end of the spring being anchored on said base and said spring serving to normally maintain coacting relationship between said deten-t and trip latch, and circuit make and break switch means also mounted on said base and including a cam equipped arm, the cam on said block-like member being engageable with the cam on said arm.

3. A thermally responsive overload switch of the type herein shown and described comprising a base plate, a pair of separate primary terminal plates mounted on one end portion of the base in side by side relation, each terminal plate beingr provided with a current input prong, a relatively stationary contact button mounted on one of said terminal plates, a current conducting heater element attached at one end with the remaining terminal plate, a pair of separate secondary ter- 1 minal plates also mounted on said base at the opposite end of the latter and in approximate longitudinal alignment with said iirst-named ter minal plates and having current output prongs, the remaining end of said heater element being attached to a complemental one of said secondary terminal plates, a normally bowed bi-metallic element also fastened at one end to said lastnamed secondary terminal plate and disposed in close proximity to said heater element, the opposite end of said bi-metallic element being free and constituting a trip-latch, a resilient arm having one end anchored on the remain-ing secondary terminal plate and having its opposite end free of attachment and provided with a contact button, the inherent resiliency of said arm serving to maintain said buttons normally engaged with each other, the intermediate portion of said arm being provided with a cam surface, a block-like member mounted for oscillation on said base and situated between the bi-metallic element and resilient arm, said block-like member having a cam at one end engaged with the cam surface on said arm and being provided at its opposite end with a shoulder forming a detent engagcable with said trip latch, and a coiled spring anchored on said base and attached to said block-like member and serving to hold said detent releasably associated with said trip latch.

4. An automatically operable overload triplatch switch of the class shown and described comprising a base plate, a primary prong equipped terminal mounted on said base plate, a complemental secondary prong equipped terminal plate mounted on said base at a point spaced longitudinally from said rst-named terminal plate and provided with an outstanding ear, a heater element attached at one end to said ear and at its opposite end to said primary terminal plate, a bi-metallic element lying alongside of said heater element and in close proximity thereto and contacting same at one end and secured at said one end to said ear, the remaining end of said bi-metallic element being free and longitudinally curved and constituting a trip latch, a block-like member mounted intermediate its ends for oscillation on said base and having a shoulder at one end constituting a detent, said detent being releasably engageable with said trip latch, and having a switch opening cam at its opposite end, a coiled spring attached at one end to the shouldered end of said block-like member and secured at its opposite end to said ear, and switch means including a resilient Contact arm having a cam surface cooperable with the cam on said blocklike member.

GEORGE E. KIRKBY.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS' Number Name Date 1,687,167 Mann Oct. 9, 1928 1,726,641 Bersted Sept. 3, 1929 1,851,144 Abramson Mar. 29, 1932 1,955,076 Ludwig Apr. 17, 1934 1,968,465 Padgett July 31, 1934 2,137,134 Forstrom Nov. 15, 1938 2,242,232 Cappelle May 20, 1941 

